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Painting steel

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  • Painting steel

    I would like to paint my cut/guide caps, which are plain steel, unplated, polished 7/8" nuts. I am reluctant to use spray cans because they are so wasteful and hard to control. I'd like to use my air brush set up, but I'm reluctant to pay $15 per ounce for the paint, as advertised during a search for airbrush paints.

    I am aware that one should prep to absolutly clean, and that primer is recommended. I want a thin, tough coat. These items never see anything but fingers, so chipping and scuffing is not a problem.

    Any suggestions of materials for priming, painting and thinning would be appreciated. We have the usual big-box stores, hardware stores and one Sherwin Williams store in this little burg.

    Thank you.


  • #2
    Don't give up on spray cans. I use Rustoleum Professional and get great results. Paint with their primer, and a few minutes later (while primer is "tacky") a top coat. Another top coat in 15-20 minutes and you're done. Very soft for 24-48 hours, but it will get there.

    The new rustoleum pro cans do not clean when inverted so take off the tops after use and soak/claam in laquer thinner.

    and.. I have a HVLP and an airbrush sytem - way too much work to setup and clean for small jobs.


    • #3
      ...but I'm reluctant to pay $15 per ounce for the paint
      I've shot Tractor Supply enamel and craft store acrylics through my Badger airbrush with great success. I've used the Testors model paint, too. Just thin until you get the results you want. The only "airbrush paint" I have ever bought was with a 30 percent off coupon at the Michael's.

      On the other hand, if you just want to black them, you could get one of the metal blackening kits from a place like Eastwood. I have a kit I bought about 20 years ago and still use it for the odd bolt or nut. I also used the kit to blacken home made hooks for a pot rack I made for the kitchen.

      Last edited by flathead4; 05-03-2012, 11:20 PM.
      Tom - Spotsylvania, VA


      • #4
        I think I should expand on this. A production run is 50 units. That is 100 nuts. I'll be doing a production run once a month. The volume therefore is enough to justify the setup and after clean time.

        I'll do some research on the metal blackening you mentioned. I have tried bluing them, but the results aren't to my liking and I don't have a hot blue can.



        • #5
          Get one of the cheapo HF powder coat guns, some Eastwood powder and a free discard oven. You'll get a tough finish in less than an hour.


          • #6
            Get the parts throughly clean, spray on several thin coats, and then if your wife/girlfriend is agreeable, open the kitchen windows and bake the parts at 300 F for about an hour.

            The paint will outgas, but after cooling down, it wil have a durable finish. I use this method for metal motorcycle parts. It's really tough, and paint stripper has difficulty removing it.


            • #7
              Take care with 300F.. make sure the paint can handle it. Some is only 200F. A cardboard box and a ceramic heater can suffice.

              If you really want to bake it, find some true baking enamel and follow the manfs recommended temperatures.

              100 nuts will take a minute or two total to spray each coat, at most


              • #8
                Originally posted by Mike Folks
                Get the parts throughly clean, spray on several thin coats, and then if your wife/girlfriend is agreeable, open the kitchen windows and bake the parts at 300 F for about an hour.

                The paint will outgas, but after cooling down, it wil have a durable finish. I use this method for metal motorcycle parts. It's really tough, and paint stripper has difficulty removing it.
                I've used this method on quite a lot of things.
                I use Rustoleum's Professional line, and limit it to 240 degrees or so.

                I've done paintball markers that don't show a scratch after me sliding around with them.

                I do believe Rustoleum sells their Professional paint in smallish cans now, if you prefer to airbrush it. Just thin it appropriately.


                • #9
                  Being wholly uneducated in airbrushing I have to say that years ago (1977) I had a Dodge van with a scratch in it's new paint. Not knowing better I bought a quart of the correct paint for the vehicle, thinned it and used an air brush to touch up the scratch. When finished you couldn't find the scratch, the paint lasted well until about 1984 or so when someone hit the van in the back and I had the whole thing painted. The air brush wasn't any worse for the wear after using regular automotive paint in it either.
                  So, maybe airbrush specific paint isn't necessary?
                  Last edited by firbikrhd1; 05-04-2012, 12:30 PM.


                  • #10
                    I've tried most of the "cold black" systems and haven't had any success with them, in terms of getting a finish that's anywhere close to the appearance and durability of real black oxide.

                    If you search "cold black" on the Practical Machinist forum you'll see some discussion of these systems.

                    Krylon spray bombs and a bake at 200 degrees (we have a toaster oven dedicated in the shop for this purpose) is what we do now for small runs of small parts, for larger runs we have a real black oxide put on them.

                    We made our own spray booth for these spray jobs, basically just a big plywood box with a false back that holds furnace filters, a blower mounted on the true back sucks air through it and vents it out through a large (12") hose vented outside the shop. If you search on spray booths you'll see some examples of what I'm talking about.

                    Paul T.


                    • #11
                      A small paint brush will work with most paints even watercolours .Don't be conned by hard selling ads to the contrary .On metal I always use enamel pait about £6.99 ish per small ish tin about 250ml it works great the kind I use is (I think ) cp90 or something like it. Alistair
                      Please excuse my typing as I have a form of parkinsons disease


                      • #12
                        I would think depending how "polished" they are you might need to rough them up a little for the paint/primer to bite in. I would also say that powdercoating might be the way to go, you can buy a gun for pretty cheap and since you are doing small parts you might get by with just a toaster oven and do them in a couple of batches.


                        • #13
                          Instead of filling your oven with toxic chemicals, Just get those cheapo 500W halogen lamps and point it directly at the surface within a foot or two after painting. The IR will cook the paint hard (Spray paints, Not 'bake on' powder coats) within 24 hours and it offgases greatly without the need to heat up a huge area or make some dangerious cardboard box+heater arrangement. Can be done in the garage.

                          That said, those 500W bulbs are a fire hazard in themselfs, don't have anything flamable near the bulb or near where the stand could be knocked over by pets or children.
                          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                          • #14
                            As others have recommended I also say go with one of the cheap powder coat systems. I have an old electric oven I use as my dedicated powder coat oven. Two things, don't ever use it for food again and do not use a gas oven, electric only.

                            For the prep, hit it with a sand blaster to give the paint something to grab.


                            • #15
                              The halogen lamp method will work, but a big advantage of the toaster oven approach is that they have regulated temperatures and are also more efficient as they contain the heat, plus they're cheap. With the Rustoleum and Krylon spray cans we use you don't want to get temp over 250 F or so.

                              The little racks they have inside the ovens also work well for our parts. Also there are a lot of different sizes, all pretty affordable, for $100. you can get a pretty big one and you can get them with timer's so its just "set and forget".

                              I'm looking at a part that we cooked this morning and it came out really nice. It was 1018 steel, machined, then cleaned in Acetone (no more lacquer thinner here in Kalifornia).

                              It was then spray bombed with a single coat of Rustoleum gloss black enamel and baked in the oven at 250F for about an hour.

                              It came out really nice, definitely much tougher than without any baking.

                              We have a real problem with paints here in Kalifornia in that they have taken pretty much all of the solvents out of them so they never really get hard, so baking is the only way to go, otherwise you can totally dent the paint with light pressure with your fingernail, even after several days.

                              The baking does knock some of the gloss off compared to an unbaked part but I actually prefer it, somehow it looks more professional than the fully gloss look before baking, it looks more like a powder coating.
                              Last edited by PaulT; 05-04-2012, 08:06 PM.